1. Technical Field
This invention relates to factory automation equipment, and more particularly to an improved ball valve insertion assembly having a safety interlock for enabling safe withdrawal of a sensor from a process fluid without requiring cessation of process fluid flow.
2. Background Information
Throughout this application, various publications, patents and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure.
Sensors of various types are routinely used in factory automation systems to measure parameters of process fluid flow. For example, DolpHin™ Series pH or ORP (Oxidation-Reduction Potential) sensors (Foxboro® Company of Foxboro, Mass.) or any number of other conventional sensors, such as conductivity and resistivity sensors, are often used to track and manage the quality of fluid flow in facilities ranging from petroleum refineries to pharmaceutical and chemical processing facilities.
These processes tend to involve highly complex systems of fluid flow, which may be particularly difficult and expensive to start and stop. Indeed, considerable effort is expended to ensure continuous operation of such processes, since even relatively short periods of operational downtime may represent tens, or even hundreds of thousands of dollars of lost revenue. Accordingly, a desirable capability is that of removing sensors for servicing, e.g., calibration, cleaning, or replacement, without having to terminate the process flow.
Ball valve insertion (BVI) assemblies have been developed and widely used to provide this capability. BVI assemblies serve as ports through which the sensors may be conveniently inserted into the process flow, and subsequently withdrawn therefrom in a three-step operation which includes retracting the sensor from the flow, isolating the assembly from the process, and then physically removing the sensor from the assembly, e.g., for servicing or replacement. A shut-off valve is generally used to isolate the assembly. Accordingly, this approach enables one to service and replace sensors without any process downtime.
While these BVI assemblies represent a significant improvement over prior approaches, there is room for improvement. As with any process penetration, leaks sometimes occur. Moreover, in spite of adequate instructions and warning labels, users may incorrectly execute the three-step sensor removal process, and inadvertently attempt to withdraw and remove a sensor without first closing the ball valve to isolate the sensor from the process flow. Such a failure may result in a fluid release.
While in some instances a fluid release may be relatively benign, in other instances, such as in the event the process fluid is caustic or hazardous, a release may be particularly undesirable, potentially necessitating costly cleanup and reporting efforts.
Thus, a need exists for an improved ball valve insertion assembly that effectively prevents a sensor from being retracted and removed prior to actuation of the ball valve.